Solvents Drying and Drying Agents Properties of solvents and methods used for drying them with specific drying agents
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Removing water from Solvents There are various ways of removing water and other impurities from a solution. This can become a major task once the used reagents are also sensitive towards water e.g. Grignard reagents or enolates. If water is one of the products, it also has a detrimental effect on the yield and/or reaction rate. In those cases, drying agents like activated alumina¹, calcium hydride (CaH2 ), sodium metal (in combination with benzophenone which forms a dark blue ketyl radical), lithium aluminum hydride (LiAlH4 ) or phosphorous pentoxide (P 4 O10 ) are used to chemically destroy the water. The drying agents commonly used in the organic laboratories are the anhydrous forms of calcium chloride (CaCl2 ), sodium sulfate (Na2 SO4 ) Calcium sulfate (CaSO4 (as Drierite) and magnesium sulfate (MgSO4 ). Organic liquids are considered to be wet if they contain water,but the organic liquid will still be a liquid after it is dried.
Activated Alumina Activated alumina ¹ is a very porous form of aluminum oxide of high surface area which adsorbs liquids and gases without any change in form. Activated alumina will not soften or disintegrate when immersed in liquids. Activated alumina may be regenerated to its original adsorption efficiency by heating to a temperature between (177-316°C). Activated alumina can be used for: Reconditioning of mineral oils like transformer or insulating oils. Removal of oil vapor mist from compressed air. Drying of organic liquids to a moisture level of 10 ppm or below. Drying of various liquids such as Benzene, Carbon, Tetrachloride, Chlorobenzene, Ethyl Acetate, Transformer oil, Vegetable oils etc.
Solvents drying guide
USE ONE OF THE FOLLOWING DRYING AGENTS
Anhydrous forms of potassium carbonate; anhydrous magnesium or calcium sulphate; quicklime.
Alkyl halides Aryl halides
Anhydrous calcium chloride; anhydrous forms of sodium sulphate, magnesium sulphate, or calcium sulphate; sodium pentoxide.
Saturated and Aromatic hydrocarbons
Anhydrous calcium chloride or sulphate; metallic sodium; phosphorus pentoxide.
Anhydrous sodium sulphate; anhydrous magnesium or calcium sulphate.